Aerosol type dispensers are well known, and they generally comprise a container containing the product to be dispensed in liquid form, and a propellant at least part of which is in the gaseous or vapor phase for exerting pressure on the liquid product for forcing the liquid product through a dip tube to a dispensing valve means mounted on the container. Upon actuation of the valve means to open the valve means, the liquid is forced through the valve means and is dispensed in the form of a spray, usually mixed with some of the propellant.
Heretofore, the propellants which have been used have been the so-called high pressure propellants, such as the fluorinated hydrocarbon known under the trademark Freon. These propellants are inert to a large number of products which it is desired to dispense from dispensers of this type, and have characteristics with respect to their vapor pressure and temperature which are advantageous for use as propellants for dispensing liquid products at ambient temperatures and with good spray patterns and droplet size.
However, one problem with the aerosol dispensers in which these propellants are used is that they must be built with sufficient strength to contain the high pressure gas, which is normally in the range of 90 to 100 psi. Pressures of this type have been necessary to keep the propellant in liquidified form in solution with the product and to provide a sufficient pressure for dispensing the product when the container is first filled and has a relatively small vapor space within the upper part of the container. Further, such pressures are necessary in order to insure that there is sufficient pressure in the container when the product is nearly exhausted to continue dispensing the product at the desired dispensing rate.
A second problem created by the relatively high pressure of the propellant is the problem of the safety of the containers. Because they contain such a high pressure, they must be handled carefully, particularly with respect to storage in high temperature locations, and because the pressure within the container is appreciable, even after all the product has been dispensed, special precautions must be taken in disposing of the containers to prevent explosion, for example, if they are incinerated.
Another problem which has recently arisen in connection with the use of Freon is the problem of the toxic and environmental effects of the Freon itself. It has recently been found that Freon can have serious effects on the respiratory reflexes, therefore making the product dangerous to inhale. This is a serious deficiency for products such as hair sprays and the like which are used in the vicinity of the nose and mouth. The environmental effect of the Freon has not yet been conclusively provided, but sufficient information is available to make packagers of products to be dispensed by dispensers of this type wary of the continued use of Freon as a propellant.
It has been speculated for some time that butane could be used as a low pressure type propellant, provided that the dispensing of products by means of butane can be controlled properly. However, the valve mechanism for controlling the dispensing of products with the high pressure propellants has been found to be unsatisfactory for the dispensing of a liquid product with butane as the propellant.
The art of aerosol type dispensers would be considerably advanced if a valve mechanism could be devised which could dispense a liquid product with butane as a propellant, since the container would then have to resist only a relatively low pressure on the order of 15-20 psi, and could accordingly be made somewhat less expensively, could be handled and shipped without danger, and could be disposed of without danger. Moreover, butane is not believed to have any environmental effects of the nature of those attributed to Freon.